The present invention relates to a laser data recording method with which data is recorded on a data recording material by scanning and modulating a laser beam.
Recently, a variety of laser data recording devices have been proposed in the art. Of these devices, a laser data recording device using a heat mode recording material is attractive because it does not require processing and real time recording is effected therewith. Such a device has been employed in recording original discs for a laser COM or a video disc.
In a heat mode laser data recording process, the recording medium absorbs a laser beam and converts its energy into thermal energy which induces physical or chemical changes in the medium so that detectable variations such a fusion, evaporation, deformation and phase changes are caused in the medium. Such a laser data recording process is specific in that it has a threshold characteristic, that is, a minimum laser power must be applied to effect the change. As a recording material of this type utilizing a thermal effect has a generally low sensitivity, it is necessary to provide a laser of considerably great power.
It is well known in the art that the amount of energy required for recording data on a heat mode data recording material depends on the recording speed. The sensitivity is improved if the recording sheet is subjected to exposure with a high illumination intensity for a short time. One method of subjecting the recording sheet to exposure with a high illumination intensity for a short time is to reduce the diameter of the laser beam and to increase the scanning speed.
As an example, with regard to a recorded image formed with 2000 scanning lines with a pitch of 5.mu. and a recorded image formed with 4000 scanning lines with a pitch of 2.5.mu. with the laser beam diameter reduced by half and with the scanning speed doubled with respect to the former, if the laser power is constant in both cases, then the same energy is applied to a point on the recording material in both cases. However, the intensity of illumination is increased four times and the exposure time is decreased to a quarter in the latter case.
Accordingly, in the latter case, the sensitivity is increased, and the laser power can be reduced as much as the increase of the sensitivity. However, it should be noted that this requires the laser beam scanning optical system to increase the optical resolution and the scanning speed and accordingly it is necessary to employ a relatively expensive optical system.
Accordingly, an object of the invention is to make it possible to efficiently record data on a heat mode data recording material with a laser beam without the above-described economical and technical difficulties.